Category: X-linked Adrenoleukodystrophy (X-ALD)

X-linked adrenoleukodystrophy (ALD) is a genetic disorder that affects the nervous system and adrenal glands. It is caused by mutations in the ABCD1 gene that lead to the accumulation of very long-chain fatty acids (VLCFA) in the body. These fatty acids build up in various tissues, including the adrenal glands, spinal cord, and brain, causing damage. Boys with ALD are typically healthy at birth, but about half will develop adrenal insufficiency and about a third will develop cerebral ALD (CALD) by the age of 10. In adults, both men and women can develop a condition called adrenomyeloneuropathy (AMN), which progressively affects the spinal cord.

Hematopoietic stem cell transplantation (HSCT) can halt the progression of CALD if performed early, but early diagnosis is crucial. Newborn screening (NBS) has greatly improved the care of boys with ALD by allowing early detection and intervention, which can prevent irreversible damage. In the U.S., more than 44 states have included ALD in their newborn screening programs, and other countries such as Taiwan and the Netherlands, have initiated ALD newborn screening.

Despite the success of newborn screening in identifying boys at risk for ALD, there are challenges. One important issue is the high rate of identification of variants of uncertain significance (VUS) in the ABCD1 gene. These VUS can be difficult to classify as pathogenic (ALD) or benign (no ALD), complicating diagnosis and management. This uncertainty can lead to unnecessary medical procedures and anxiety for families.

To address this, we have developed a new type of probe, called PeroxiSPY, that allows live imaging of peroxisomes (cell structures involved in fatty acid metabolism). These probes can help identify functional abnormalities in peroxisomes and are dependent on ABCD1-3 transporters. By designing ABCD1-specific PeroxiSPY probes, we aim to develop a test that can accurately measure the function of the ABCD1 protein. This would help distinguish between benign and pathogenic variants of the gene, improving the accuracy and utility of newborn screening programs for ALD.

The project aims to generate ABCD1-specific PeroxiSPY probes that will allow precise measurement of ABCD1 function using advanced microscopy techniques. This will be tested in cells derived from ALD patients and individuals with VUS in ABCD1. The availability of a rapid and sensitive assay to define whether a VUS is pathogenic (causing ALD) or benign (not causing ALD) is of paramount importance to families.

X-linked adrenoleukodystrophy is a genetic disease affecting mostly young male patients. In its severest form, patients develop a fulminant inflammatory destruction of central nervous system white matter, areas where all descending nerve fiber tracts are contained. Untreated, patients suffering from this disease mostly die within months to few years. The only effective therapy for halting the progression is an early transplantation of hematopoietic stem cells. Though progression often can be stopped this way, any disability that patients had accumulated before treatment recovers very poorly. This is in harsh contrast to another inflammatory disease affecting the white matter, multiple sclerosis. Here, patients often recover very well after an inflammatory and demyelinating bout. The reasons for this difference are not yet understood.

In this project, the team strive to investigate the reasons underlying the apparent lack of regeneration in X-ALD. They will use autopsy tissue from human patients who died of X-ALD as a starting point and let their research be guided by a careful re-examination of pathologic changes in this tissue. In addition, they will use novel proteome and transcriptome techniques that allow a very detailed investigation of molecular alterations in the tissue. In this way the researchers strive to identify novel molecular and cellular pathways of the disease that could be manipulated in order to improve clinical recovery in X-ALD. Furthermore, in their novel detailed analysis of the human histopathology they hope to provide a valuable tool also for other researchers working in the field.

Project financed by ELA up to: 72 375 €

With a combined incidence of 1:14,700, X-ALD is the most common monogenetically inherited leukodystrophy. The disease is caused by mutations of the peroxisomal very long-chain fatty acid transporter ABCD1 that normally imports very long-chain fatty acids into the peroxisome for degradation. Accordingly, loss of ABCD1 function results in accumulation of very long-chain fatty acids in the plasma and body fluids of affected patients. X-ALD shows a striking phenotypic heterogeneity with inflammatory cerebral X-ALD (CALD) being the most severe form. In order to be treatable by bone marrow transplantation or gene therapy, CALD has to be recognized in its earliest stages.

The ultimate goal of this research project is to identify an easily accessible blood biomarker indicative for onset and progression of CALD. If successful, the identified blood biomarker could provide valuable information for decisions on clinical interventions and could also be used as treatment efficacy marker in clinical trials targeting CALD.

Project financed by ELA up to: 29 000 €